std::sort()

定义

template <class RandomAccessIterator, class Compare>
  void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);

作用:

Sorts the elements in the range [first,last) into ascending ↑(when comp is nullptr) order.

comp函数说明:

---

Binary function that accepts two elements in the range as arguments, and returns a value convertible to bool.The value returned indicates whether the element passed as first argument is considered to go before the second in the specific strict weak ordering it defines.
当函数返回true时,认为第一个参数在第二个参数之前(第一个参数的索引值小)

---

The function shall not modify any of its arguments.
This can either be a function pointer or a function object.

---

引自---cplusplus.com

实验:

源码:

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
bool comp1(int a,int b) {
    return b>a;
}
bool comp2(int a,int b) {
    return a>b;
}
int main() {
    int arr[] = {1,2,3,9,8,7};
    cout<<"sort by comp1 (ascending):"<<endl;
    sort(arr,arr+6,comp1);
    for(int i:arr) {
        cout<<i<<endl;
    }
    cout<<"sort by comp2 (descending):"<<endl;
    sort(arr,arr+6,comp2);
    for(int i:arr) {
        cout<<i<<endl;
    }
    return 0;
}

输出: